linux-kernel - Re: [PATCH v5 5/7] sched: compute runnable load avg in cpu_load and cpu_avg_load_per

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Date:	Tue, 07 May 2013 13:12:02 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Paul Turner <pjt@...gle.com>
CC:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Namhyung Kim <namhyung@...nel.org>,
	Mike Galbraith <efault@....de>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Michael Wang <wangyun@...ux.vnet.ibm.com>
Subject: Re: [PATCH v5 5/7] sched: compute runnable load avg in cpu_load and
 cpu_avg_load_per_task

On 05/07/2013 02:34 AM, Paul Turner wrote:
>> > Current load balance doesn't consider slept task's load which is
>> > represented by blocked_load_avg. And the slept task is not on_rq, so
>> > consider it in load balance is a little strange.
> The load-balancer has a longer time horizon; think of blocked_loag_avg
> to be a signal for the load, already assigned to this cpu, which is
> expected to appear (within roughly the next quantum).
> 
> Consider the following scenario:
> 
> tasks: A,B (40% busy), C (90% busy)
> 
> Suppose we have:
> CPU 0:  CPU 1:
>  A            C
>  B
> 
> Then, when C blocks the load balancer ticks.
> 
> If we considered only runnable_load then A or B would be eligible for
> migration to CPU 1, which is essentially where we are today.
> 

here is the changed patch according to Paul's comments. Is that you liked, Paul? :)

---

>From 1d7290530e2ee402874bbce39297bb1cfd882339 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@...el.com>
Date: Sat, 17 Nov 2012 13:56:11 +0800
Subject: [PATCH 5/7] sched: compute runnable load avg in cpu_load and
 cpu_avg_load_per_task

They are the base values in load balance, update them with rq runnable
load average, then the load balance will consider runnable load avg
naturally.

Signed-off-by: Alex Shi <alex.shi@...el.com>
---
 kernel/sched/core.c | 16 ++++++++++++++--
 kernel/sched/fair.c |  8 ++++++--
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 33d9a858..f4c6cac 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2536,9 +2536,14 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
 void update_idle_cpu_load(struct rq *this_rq)
 {
 	unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
-	unsigned long load = this_rq->load.weight;
+	unsigned long load;
 	unsigned long pending_updates;
 
+#ifdef CONFIG_SMP
+	load = this_rq->cfs.runnable_load_avg + this_rq->cfs.blocked_load_avg;
+#else
+	load = this_rq->load.weight;
+#endif
 	/*
 	 * bail if there's load or we're actually up-to-date.
 	 */
@@ -2582,11 +2587,18 @@ void update_cpu_load_nohz(void)
  */
 static void update_cpu_load_active(struct rq *this_rq)
 {
+	unsigned long load;
+
+#ifdef CONFIG_SMP
+	load = this_rq->cfs.runnable_load_avg + this_rq->cfs.blocked_load_avg;
+#else
+	load = this_rq->load.weight;
+#endif
 	/*
 	 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
 	 */
 	this_rq->last_load_update_tick = jiffies;
-	__update_cpu_load(this_rq, this_rq->load.weight, 1);
+	__update_cpu_load(this_rq, load, 1);
 
 	calc_load_account_active(this_rq);
 }
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2881d42..407ef61 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2900,7 +2900,8 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 /* Used instead of source_load when we know the type == 0 */
 static unsigned long weighted_cpuload(const int cpu)
 {
-	return cpu_rq(cpu)->load.weight;
+	struct rq *rq = cpu_rq(cpu);
+	return rq->cfs.runnable_load_avg + rq->cfs.blocked_load_avg;
 }
 
 /*
@@ -2946,8 +2947,11 @@ static unsigned long cpu_avg_load_per_task(int cpu)
 	struct rq *rq = cpu_rq(cpu);
 	unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
 
+	unsigned long load_avg;
+	load_avg = rq->cfs.runnable_load_avg + rq->cfs.blocked_load_avg;
+
 	if (nr_running)
-		return rq->load.weight / nr_running;
+		return load_avg / nr_running;
 
 	return 0;
 }
-- 
1.7.12


-- 
Thanks
    Alex
--
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